1. Field of the Invention
The present invention relates generally to robotic storage libraries, and specifically to determining relative positions of robotic access mechanisms that share a common axis of motion in the library.
2. Background of the Invention
Storage libraries are collections of media volumes (e.g., reels of magnetic tape) used for storing and accessing information. A typical storage library has many media volumes that contain information, drives for reading from and writing to the volumes, and some mechanism for moving volumes from their individual storage slots to a drive and back again. Modern storage libraries often employ one or more “robotic pickers” that are designed to move media volumes within the library from storage to drive and back again.
In many storage libraries, these robots are devices that move along a predetermined pathway, such as a rail that passes a specific set of media volumes. By translating the robot along the rail, various volumes can be reached and moved by the robot. Often, in order to facilitate faster access to data on volumes of the library, more than one robot is employed. In some cases, these multiple robots, or other redundant access mechanisms, may share a common axis of movement, e.g., they move along the same physical rail.
Typically, when more than one robot shares a rail or other common axis of movement, specific hardware indicators are used to identify where the robots are with respect to one another; such hardware indicators must be correctly set during robot installation, designating the relative positions of the robots. In other words, one robot of a pair will be the “right” robot while the other will be the “left” robot; if there are more than two on the rail, they will be the “second from left”, “third from left”, etc. The order must be kept straight at installation in order for the system to work correctly. Failure to install the robots in their correct relative position will result in malfunction of the storage system. Further, when a robot fails, it is often removed from the system for servicing and replaced later. In such cases, the technician must be careful to restore the robots in their correct relative positions once again, loading the robots onto the rail in the same order as they were previously. This can result in confusion and can increase the duration and frequency of service calls.
Therefore, the present state of the art would benefit from a system to determine relative positions of robots in a storage library without the use of specific hardware indicators or unique “left/right/other” robots.